Detection of corrosion-induced cracks in reinforced concrete using Rayleigh wave method

Abstract

Concrete is a widely used construction material due to its strong bonding properties and ability to promote the durability of structures. Yet, in some cases, concrete may fail to perform satisfactorily due to harsh environmental conditions that may cause structural degradation. One of the main contributors to the degradation of reinforced concrete (RC) structures is the corrosion process over a prolonged period of time. This process involves the creation of expansive corrosion products that generate tensile stress within the concrete, ultimately resulting in cracking and spalling. Thus, to extend the lifespan of RC structures and detect corrosion-induced cracks in concrete before spalling occurs, reliable non-destructive inspection technologies are required. Ultrasonic Rayleigh waves have been used to detect cracks in concrete by utilizing transmission coefficient, time of flight information, and reflections from cracks. However, the efficiency of these techniques may be constrained by the variety of concrete materials, poorly defined Rayleigh wave components and sensor coupling on rough surfaces. This report suggests an enhanced technique for detecting internal cracks in concrete caused by corrosion using Rayleigh waves. This technique is based on the observation that, when transmitted Rayleigh waves pass through cracks, their spectrum shifts with the depth of penetration varying with frequency. A Continuous Wavelet Transform (CWT) was employed to analyse the energy spectrum of transmitted Rayleigh waves and correlate the locations of internal cracks. To test the proposed method's efficacy, an RC sample was subjected to accelerated corrosion at different locations, and the proposed Rayleigh wave-based method was used to generate a corrosion damage map. Electrochemical tests were also conducted to map the corrosion current density, and the results were found to be in good agreement with the corrosion damage map generated from the proposed Rayleigh wave-based method.